You know what to do, Republican ad-makers.

In September 2010, Senate Republicans brought a resolution to the floor to block implementation of the grandfather rule, warning that it would result in canceled policies and violate President Barack Obama’s promise that people could keep their insurance if they liked it.

“The District of Columbia is an island surrounded by reality. Only in the District of Columbia could you get away with telling the people if you like what you have you can keep it, and then pass regulations six months later that do just the opposite and figure that people are going to ignore it. But common sense is eventually going to prevail in this town and common sense is going to have to prevail on this piece of legislation as well,” Iowa Sen. Chuck Grassley said at the time.

“The administration’s own regulations prove this is not the case. Under the grandfathering regulation, according to the White House’s own economic impact analysis, as many as 69 percent of businesses will lose their grandfathered status by 2013 and be forced to buy government-approved plans,” the Iowa Republican said.

On a party line vote, Democrats killed the resolution, which could come back to haunt vulnerable Democrats up for re-election this year.

Pryor, Landrieu, Begich, Hagan — all your favorite vulnerable Democratic incumbents from conservative states went face-first into the tank as usual to protect Obama’s baby and now they’re paying for it, which explains why Landrieu’s suddenly pushing a bill along the same lines as tea-party Republican Ron Johnson to re-grandfather some plans. Big question mark, though: Did Senate Democrats anticipate just how restrictive Obama’s HHS would be in writing the regulations that ended up disqualifying many plans from grandfather status? Per CNN, some Dems like Tom Harkin defended their vote against the GOP proposal in 2010 at the time by claiming that it might, in theory, end up re-grandfathering everything, which would defeat the purpose of rendering truly bad plans illegal. Instead, HHS wrote the regs so restrictively that even decent plans ended up being nuked when insurers made small changes to them. That’s why Frank Pallone was babbling about “scams” on Megyn Kelly’s show on Wednesday night: Congressional Democrats have now been reduced to claiming, surreally, that basically all of the plans that have now been canceled were “bad” and scam-like even though the media’s spent the past week interviewing consumers who wish they could have them back.

None of this excuses Pryor et al. for not anticipating what would happen but it does create political space for them potentially to say that, knowing what they know now about how HHS implemented the grandfather rules, they might have voted differently. And once they say that, future ObamaCare votes in the Senate start to look … interesting. Via the Corner, here’s Avik Roy explaining that the individual insurance market is really just a canary in the coal mine; disruption has already begun on the much bigger employer-based market, with full impact scheduled for 2015 once the “delay” in the employer mandate ends. If red-state Dems think they’re having a tough time explaining their votes now, just wait. Exit question: Roy says of O’s now infamous “if you like your plan” nonsense, ““Everyone in the health-policy community left, right, or center knew this was a lie.” How come Senate Democrats didn’t know?